What is the Difference between the PNR and the Invoices?

Invoices are either exclusively for sales or exclusively for purchases, but the PNR contains both the purchase price and the selling price for the same products or services within the same document. The PNR is used in travel companies to determine the profitability of each product based on the comparison between your purchase price for the service and its selling price to the client, thereby estimating your profitability.

For more details about the PNR, check out this guide.